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One of the myths perpetuated with radiant cooling
systems is condensation risk on the cooling surface. This would
be a real risk if there was no moisture control. Without
moisture control numerous risk factors develop such as
hydrolysis. From
Princeton University, "Hydrolysis is a chemical reaction
during which molecules of water (H2O) are split into hydrogen
cations (H+, conventionally referred to as protons) and
hydroxide anions (OH−) in the process of a chemical mechanism.
It is the type of reaction that is used to break down certain
polymers...".
Clearly you can see in Figure 1 that in this
specific study by Dr. Richard L. Corsi, paint emissions
(specifically HC-O-O) are affected by rising relative
humidity.[1] Matthews et al. noted that changing the
indoor conditions from
68°F (20°C)
and 30% relative humidity
(RH) to 79°F (26°C)
and 60% RH would
result in two to fourfold increases in formaldehyde
concentration for the same air change rate.[2] Hodgson et al
stated in their study on the topic, "This suggests that indoor
humidity has a substantial impact on formaldehyde emission rates
and concentrations." [2]
There is an exhaustive supply of research
addressing this topic and readers are encouraged to seek out
these documents for detailed study. For our purposes here, it is
enough to say once again moisture must be controlled in
habitable spaces
which ultimately enables the successful use of radiant cooling.
This content is a key component from our course,
"Integrated HVAC Engineering: Mastering Comfort, Health,
and Efficiency."
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References:
1. Relative humidity and paint emissions (HC-O-O)
adapted Richard L. Corsi, Ph.D., PE , Building Energy &
Reactivity Complex Interactions. Simple Solutions, IAQ 2013 –
Environmental Health in Low Energy Buildings – Vancouver, BC,
Canada October 17th, 2013
2. Hodgson, Alfred T., Steven J. Nabinger, and Andrew K. Persily.
2004. “Volatile Organic Compound Concentrations and Emission
Rates Measured over One Year in a New Manufactured House.”
doi:10.2172/838617. http://www.osti.gov/scitech/servlets/purl/838617. |
